SYNOPSIS

DESCRIPTION

This module provides control structures to iterate through the elements of an object that cannot be represented as list of items all at once. Objects can represent a virtual collection that is beyond the reaches of foreach, map, and grep because they cannot turn themselves into a list.

If the object can return a next element, it can use this module. Iterate assumes that the object responds to __next__ with the next element, and to __more__ with TRUE or FALSE if more elements remain to be processed. The __init__ method is called before the first iteration (if it exists), and is silently skipped otherwise. The control structure continues until the __more__ method returns FALSE (which does not mean that it visited all of the elements but that the object has decided to stop iterating). At the end of all iterations (when __more__ returns false), Object::Iterate calls __final__ if it exists, and skips it otherwise.

Each control structure sets $_ to the current element, just like foreach, map, and grep.

Mutable method names

You do not really have to use the __next__, __more__, __init__, or __final__ names. They are just the defaults which <Object::Iterate> stores in the package variables $Next, $More, $Init, and $Final respectively. This module does not export these variables, so you need to use the full package specification to change them (i.e.$Object::Iterate::$Next). If your object does not have the specified methods, the functions will die. You may want to wrap them in eval blocks.

Since this module uses package variables to storethese methods names, the method names apply to every use of the functions no matter the object. You might want to local()-ise the variables for different objects.

Before any control structure does its job, it checks the object to see if it can respond to these two methods, whatever you decide to call them, so your object must know that it can respond to these methods. AUTOLOADed methods cannot work since the module cannot know if they exist.

iterate BLOCK, OBJECT

Applies BLOCK to each item returned by OBJECT->__next__.

iterate { print "$_\n" } $object;

This is the same thing as using a while loop, but iterate() stays out of your way.